An adolescent has vague knee pain. There is tenderness and increased prominence of the tibia tubercle. Which is the most likely diagnosis?

Correct Answer: C

Rationale: Osgood-Schlatter disease presents with tibial tubercle tenderness and prominence due to traction apophysitis.

Correct Answer: D

Rationale: The distal tubule fine-tunes sodium reabsorption under aldosterone control, making it the critical site for sodium balance regulation.

Correct Answer: B

Rationale: High white blood cell counts (e.g., leukemia) cause spurious hypokalemia as cells take up potassium in vitro after blood draw.

Correct Answer: C

Rationale: Severe anemia can cause normal anion gap acidosis due to reduced oxygen delivery; others typically increase the anion gap.

Correct Answer: D

Rationale: A tiring patient indicates respiratory muscle fatigue, necessitating ventilation to prevent failure.